# Referrer

This setting operates on the same principle as the user agent filter described above but for the HTTP referrer. Cloakify will filter out all visitors whose referrer matches the specified Perl-compatible regular expression. Comparison is case-sensitive.

Common use cases:

Filtering visitors with an empty referrer:

^$

Filtering visitors who didn't arrive via an advertising link. An example for Google Ads:

^(.(?!(google[.])))*$

Note! Improperly formed regular expressions can lead to false positives and filtering out large amounts of legitimate traffic. Use this setting only if you know what you're doing.